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About the Year of Light

The International Year of Light is a global initiative which will highlight to the citizens of the world the importance of light and optical technologies in their lives, for their futures, and for the development of society. It is a unique opportunity to inspire, educate, and connect on a global scale.

Sunset (Lensing) Iowa, USA

Red Sunset Moorea-Maiao, Windward Islands, French Polynesia

Why do sunsets often appear red? The answer has to do with a particular behavior of light: scattering. When sunlight strikes certain atoms and molecules in the Earth's atmosphere, some of the light is absorbed and re-emitted as a light wave in various directions. This means less of it reaches us on the surface. Due to the composition of the planet's atmosphere, the shorter wavelength colors of the rainbow are scattered more. Our Sun gives off light in all colors, but its light is most intense in yellow (which is why it appears yellow when we see it midday). Photos from above the atmosphere show a white sun, so the sun's yellow appearance is the result of scattering. At sunset, the sunlight must pass through more of the Earth's atmosphere and, thus, more of the yellow wavelength is scattered away. This leaves us frequently with a reddish orange sunset to admire.
Image Credit:
J L Spaulding, creative commons licenseview and download image here.

Shadows Of Antelope Canyon, Arizona, US

Shadows are a familiar experience for most of us. Any time an object blocks the light from another source, it forms a shadow. In this photograph, we see shadows on the spectacular walls of Antelope Canyon in Arizona as sunlight streams through an opening above. But did you know all of the places that shadows occur? For example, larger objects such as the Earth and the Moon can cast shadows during eclipses. Shadows can also happen with different types of light from radio waves up to more energetic X-rays and gamma rays. The nature of a shadow depends on both the object and the light that it is blocking.
Image Credit:
J L Spaulding, creative commons licenseview and download image here.

Sandstone Mesas With Rainbow

Sunlight is made up of a mixture of many wavelengths of light. Each visible wavelength is perceived as a different color, with violet having the shortest wavelength, and red the longest. When sunlight enters a raindrop, its path is bent; the light is "refracted". Each wavelength is bent slightly differently, with shorter wavelengths bent more than longer ones. This rainbow is caused by light being refracted (bent) when entering a droplet of water, then reflected inside on the back of the droplet and refracted again when leaving it. This causes the combined colors of sunlight to spread out into the familiar red, orange, yellow, green, blue, indigo, and violet of a rainbow. A person viewing this light from the viewpoint where the light has been reflected is treated to the spectacular view of a rainbow, like the one seen here above the mesas in Utah.
Image Credit:
David Parker/ Science Photo Library
view and download image here.

Lake Reflections Tso Moriri Lake, India

Most objects do not emit light. Rather, they reflect it from a source like a light bulb or sunlight. This common process allows us to see these things that are all around us. In fact, one of the fundamental laws of the physics of light involves reflection. Reflection consists of two rays: an incoming or 'incident' ray and an outgoing or 'reflected' ray. All reflected light obeys the rule that says the incident ray strikes a surface at the same angle that the reflected ray bounces away from it. In the case of a smooth surface like a mirror or, in the case of the photograph, the calm top of a lake, a clear identical image is produced.
Image Credit:
Prabhu B Dossview and download image here.

This website was developed by Lightsources.org, a collaboration between communicators from light source facilities around the world.

IYL2015 is a global initiative adopted by the United Nations to raise awareness of how optical technologies promote sustainable development and provide solutions to worldwide challenges in energy, education, agriculture, communications and health.